As is well known, with most of the digital data signal processors according to the prior art, numbers of a two digit binary system using {0, 1} digit set are processed as digital data signals, and this is the same with A/D converters and D/A converters converting analog signals to digital data signals and vice versa.
Further, as is well known, with a part of digital computers, 2-based three digit redundant binary numbers using a three signal set {-1, 0, 1} as one digit are used for improvement. That is, to shorten operation time by an expected smaller frequency of carry digits than two digit binary numbers.
The Japanese Patent Application No. 133927/1998 (U.S. application Ser. No. 09/312,347) by the inventor has verified a one-to-one correspondence existing between the HEN2 (which is a combination of such signals, selected from a 2-based three digit redundant binary number with either one signal of three digits {n, o, p} each expressing a value {-1, 0, 1} as a one-digit signal. At least one of two adjacent digits at any digit position of one or more digits expresses zero (the signal "o")) and 2-based two digit binary numbers using {0, 1} digit set. This correspondence may allow analog signals to be converted to digital data signals having two digit binary numbers and then to digital data signals of the HEN2 type with one-to-one correspondence. Further, the correspondence may allow digital data signals of the HEN2 to be converted to digital data signals of the two digit binary number with one-to-one correspondence, and then to analog signals. But, either case must go through digital data signals of the two digit binary numbers, thus resulting in a longer time for conversion and necessitating a reduction of conversion time.
Further, since HEN2 and two digit binary numbers are different in their value ranges even with the same number of digits, mutual conversions between digital data signals of HEN2 and analog signals by way of digital data signals of the two digit binary numbers may not make full use of the characteristics of the HEN2 as digital data signals, thus necessitating a direct conversion between analog signals and digital data signals of HEN2.